Microvolt level signals often need to be amplified with large gains before they can be digitized by an analog to digital converter (ADC). In the presence of high amplifier gain needed to amplify the microvolt level signals, the amplified offset can be so large as to force the amplifier output to reach a minimum or maximum level where it is no longer responsive to the input signal. For complementary metal-oxide semiconductor (CMOS) circuits built in modern integrated circuit processes and operating in low radiation environments, amplifier offsets can be kept reasonably small without auto-zeroing. However, if the circuit were to accumulate sufficient amounts of ionizing radiation dose, the circuit's offset could increase significantly due to changes in the CMOS transistor threshold voltages. Space based instruments can be exposed to extreme radiation such as exists in the Jovian orbital system, accumulating ionizing doses in excess of 3 Mrad (Si). Amplifier offsets can thus vary by at least several millivolts from an ideally near zero voltage design point and eventually cause amplifier saturation.
Chopper stabilization is an established method for reducing the offset and 1/f noise of an amplifier. On its own, the technique is effective as long as the amplifier output is not saturated which can occur if the both the amplifier gain and its offset are large. Thus chopper stabilization techniques of and by themselves may not be sufficient to reduce amplifier offset at high gains. Therefore, an adaptive technique must be employed.